Unsaturated epoxy ester resins are used as coatings, because they excel in chemical resistance, water resistance, mechanical property, and bondability. They are widely used as the base resin of liquid photo solder resist materials for the production of printed circuit substrates. Unsaturated epoxy ester resins in which a part of the glycidyl side group has been carboxylated are particularly useful because they are soluble in aqueous alkaline solution, and, therefore, do not require use of organic solvent for development. Furthermore, since mechanical property and bondability may be improved, for example, by combining with epoxy resin, this resin is presently being used for preparing liquid photo solder resists. However, since organic solvent such as aromatic compounds or aliphatic esters are still used to liquefy the resin composition, there are associated health, safety and environmental concerns.